Vacuum cleaner with nozzle height adjusting mechanism

ABSTRACT

An upright vacuum cleaner having a suction nozzle at the front of an access plate mounted on the bottom of the chassis. At least four nozzle height positions relative to the surface of the floor to be cleaned is obtained by manually indexing an adjusting lever pivotably mounted on one side of the cleaner and having a pin mounted in one leg thereof. The rear wheels of the cleaner are rotatably mounted on the ends of a crank type offset axle pivotably mounted on the bottom of the cleaner frame. Two front wheels of the cleaner are each mounted on one leg of separate Ushaped axles, each having its other leg pivotally supported on opposite sides of the bottom of the frame. Linage assemblies connect each end of the rear axle to the respect wheel mounted leg of each front wheel axle. The linkage on the adjustable lever side of the cleaner includes a slot for receipt of the lever pin so that as the lever is pivotably moved the pin drives the linkage, thus causing the front and rear axles simultaneously to pivot on their respect journals. This effects a change in the relation between all four wheels and the cleaner housing, thereby raising or lowering the nozzle relative to the floor.

United States Patent [191 Clowers et al.

[451 Jan. 30, 1973 [54] ACUUM CLEANER WITH NOZZLE HEIGHT ADJUSTING MECHANISM [75] Inventors: Earl R. Clowers; Walter G. Azelkas,

both of Anderson, S.C.

[73] Assignee: The Singer Company, New York,

[22] Filed: March 29, 1971 [21] Appl. No.: 128,755

Primary Examiner-Edward L. Roberts Assistant ExaminerC. K. Moore Attorney-Marshall J. Breen, Chester A. Williams and Alan Ruderman [57] ABSTRACT An upright vacuum cleaner having a suction nozzle at the front of an access plate mounted on the bottom of the chassis. At least four nozzle height positions relative to the surface of the floor to be cleaned is obtained by manually indexing an adjusting lever pivotably mounted on one side of the cleaner and having a pin mounted in one leg thereof. The rear wheels of the cleaner are rotatably mounted on the ends of a crank type offset axle pivotably mounted on the bottom of the cleaner frame. Two front wheels of the cleaner are each mounted on one leg of separate U- shaped axles, each having its other leg pivotally supported on opposite sides of the bottom of the frame. Linage assemblies connect each end of the rear axle to the respect wheel mounted leg of each front wheel axle. The linkage on the adjustable lever side of the cleaner includes a slot for receipt of the lever pin so that as the lever is pivotably moved the pin drives the linkage, thus causing the front and rear axles simultaneously to pivot on their respect journals. This effects a change in the relation between all four wheels and the cleaner housing, thereby raising or lowering the nozzle relative to the floor.

7 Claims, 5 Drawing Figures PATENTEDJAN 30 I973 SHEET 1 BF 2 R. Clowers and Earl BY alter G. Alelkds an a h A;

- TTORN EY VPATENTEDJMOIQB 3713.185

SHEET 2 BF 2 INVENTORS Earl R. Clowers and BY Walter G. Azelkas wamsss M d/W w- 7mm AT ORNEY VACUUM CLEANER WITII NOZZLE HEIGHT ADJUSTING MECHANISM BACKGROUND OF THE INVENTION This invention relates to vacuum cleaners and more particularly to a vacuum cleaner of the floor cleaning type having means for raising and lowering the nozzle depending on the type of floor covering being cleaned.

Vacuum cleaners of the floor cleaning or upright type generally include a chassis having a nozzle at the bottom thereof through which air is suck by an air moving motor-blower unit, a rotary brush mounted adjacent to the nozzle for contacting the floor surface to agitate and loosen the dirt so that it may be sucked free of the surface, and wheels mounted at the front and rear of the chassis for supporting the cleaner for rolling on the floor. These vacuum cleaners are called upon to clean many different kinds of modern floor coverings varying in pile thickness from the short thin outdoor or patio type to the long deep shag type. In order to clean these various floor surfaces effectively it is known to vary the nozzle height to locate the nozzle at a level above the surface that provides the proper suction and flow path for the particular type floor covering or surface being cleaned.

Nozzle height adjusting mechanism are known which raise or lower the nozzle by raising or lowering either the front or the rear wheels relative to the chassis, thereby to tilt the chassis about the non-adjustable wheels. However, the variation in pile thickness of modern floor coverings is so extreme that if only one set of wheels are adjusted the chassis must tilt through a wide angle between the extremes of the desired nozzle height. Inasmuch as large variations in the chassis angle relative to the floor have adverse affects on the suction capability of the nozzle and the beater action of the brush, poor cleaning results occur at these extreme conditions. For example, in those cleaners designed with adjustable rear wheels only the chassis pivots about the front wheels and the rear of the chassis undergo wide variations in elevation. When such a cleaner is operated on low pile carpeting, especially outdoor type carpeting and bare floors, the rear of the chassis rises, and because of the steep angle the brush may throw the loosened dirt back too low for the nozzle effectively to suck it in. Furthermore, when such a cleaner operates on high pile carpeting the rear of the chassis may drop too low and drag on the floor surface thus causing extra wear on the carpeting. In those cleaners having adjustable front wheels only, the front end of the chassis may tend to dig into the carpeting on low pile carpeting while the rear end may dig in on high pile carpeting. Moreover, in both types of arrangements, the silhouette of the chassis when the front end is raised for cleaning high pile carpeting is such that it may not get under furniture for proper cleaning.

SUMMARY OF THE INVENTION The primary object of the present invention is to provide an improved nozzle height adjusting mechanism for a vacuum cleaner of the above type, whereby the nozzle height may be varied between wide limits while maintaining a greatly reduced angular variation of the chassis relative to the floor.

Another object of the invention is to provide an onthe-floor vacuum cleaner having an improved nozzle height adjusting mechanism which raises and lowers the nozzle by varying the relationship of the chassis to the front and the rear wheels.

A further object of the invention is to provide an improved nozzle height adjusting mechanism in a vacuum cleaner of the type which is supported on front and rear wheels, whereby the axes of rotation'of all the wheels may be selectively varied relative to the nozzle.

A still further object of the invention is to provide an improved nozzle height adjusting mechanism in a vacuum cleaner of the type which is supported on front and rear wheels, whereby the front and rear wheels simultaneously are pivoted by a single control member relative to the nozzle, the front wheels rising while the rear wheels lower and the front wheels lowering while the rear wheels rise.

Accordingly, this invention provides a vacuum cleaner comprising a chassis having a suction nozzle therein arranged for floor cleaning, a pair of front wheels and a pair of rear wheels which support the cleaner for rolling on the floor. The rear wheels are mounted on offset ends of a rear axle formed with the central portion which is journaled in the rear of the chassis. The front wheels are each mounted on one leg of separate U-shaped axles, each having its other leg pivotally supported on opposite sides of the bottom of the frame. Linkage assemblies connect each offset end of the rear axle to the wheel mounted leg of a respective front wheel axle. An adjustable lever is pivotably mounted on one side of the chassis and operatively engages the linkage on said side so that as the lever is pivotably moved the linkage is driven to cause the front and rear wheels simultaneously to pivot in the respective journals, the front wheels rising when the rear wheels lower and the front wheels lowering when the rear wheels rise-relative to the chassis. This affects a change in the relation between all four wheels and the chassis, thereby raising or lowering the nozzle relative to the floor while maintaining a small angular variation in the attitude of the chassis.

BRIEF DESCRIPTION OF THE DRAWINGS The particular features and advantages of the invention as well as other objects will become apparent from the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is a bottom plan view of a vacuum cleaner embodying the present invention;

FIG. 2 is a cross sectional view taken substantially along line 2-2 of FIG. 1, illustrating the lowest nozzle height position in solid lines and the highest nozzle height position in dotted;

FIG. 3 is a perspective view of the nozzle height adjusting mechanism removed from the cleaner chassis to show details of construction, and showing the chassis access plate including the nozzle opening in phantom;

FIG. 4 is a cross sectional view taken substantially along line 4-4 of FIG. 1; and

FIG. 5 is a cross sectional view taken substantially along line 5--5 of FIG. 2, illustrating the adjustment lever assembly.

DESCRIPTION OF PREFERRED EMBODIMENT Referring now to the accompanying drawings, wherein like reference numerals denote similar parts throughout the various views, there is disclosed the working portion of a vacuum cleaner of the type known as a floor cleaner, or upright vacuum cleaner. A cleaner of this type is shown in its entirety in U.S. Pat. No. 3,163,439 which issued on Dec. 29, 1964 to the same assigneeas the present invention, and since the propelling handle and dust bag are conventional and form no part of the present invention and are not necessary for a clear understanding thereof, reference should be had to said patent for a disclosure of the complete cleaner.

The vacuum cleaner includes a chassis 20, on the top of which is secured a hood 22. Formed in the bottom of the chassis is a central recess 24 within which is housed an electric motor (not shown), and a pair of recesses 26, 26 for housing a pair of fan impellers (not shown). The motor drives the fan impellers which communicate with a rearwardly open common discharge duct 28 to which is secured a dust bag assembly, as illustrated in the aforesaid U.S. Pat. No. 3,163,439. An access plate 30 having a pair of apertures 32 and 34 disposed therein is releasably secured to the bottom of the chassis. The access plate 30 includes in the front edge thereof three slots 36 which are adapted to register with respective tabs 38 formed on the bottom leading edge of the chassis. A pair of retaining clips 40, movably secured by screws 42 to shoulders 44 on opposite sides of the bottom of the chassis, and a latch 46 on the chassis which cooperates with a lug 48 on the access plate, operate to secure the access plate to the chassis when the tabs 38 are in proper registration with the slots 36. The vacuum cleaner inlet nozzle, which is defined by the apertures 32 and 34, communicates with the fans by means of air passages defined between the bottom of the chassis and a pair of rearwardly extending arms 50 of the access plate to produce a suction at the nozzle inlet when the motor is in operation. A conventional rubber bumper 52 aids in sealing the access plate and chassis to minimize the suction losses between the fan and the nozzle inlet. The fan exhaust air is discharged through the duct 28 and into the dust bag in the conventional manner. A rotary floor brush assembly 54 including a spirally disposed brush 56 is mounted in the nozzle above the openings 32 and 34 and includes a pair of bearings 58 at its extremities positioned in corresponding mounting plates 60 at opposite sides of the chassis so as to contact the floor surface when the cleaner is in the operating position as shown in FIG. 2. An endless belt 62 drives the brush assembly from a spindle (not shown) on the motor fan shaft.

A pair of downwardly depending bosses 64, each having a bearing recess 66 formed therein, are cast on opposite sides of the rear of the chassis. A rear axle 68, including a central portion 70 having offset end portions 72 and 74, is journaled on the central portion in the bearing recesses 66 and pivotably maintained therein by a retaining plate 76 which is secured to the chassis by screws 78 threaded into the bosses 64 and screws 80 which are threaded into a pair of bosses 82 cast on the bottom of the chassis. Rotatably mounted on the free extremity of each offset end 72 and 74 is a respective rear wheel 84 and 86. As in the aforesaid U. S. Patent, turning of the rear axle about the central portion 70 results in a raising or lowering of the rear wheels 84 and 86 relativeto the chassis. in other words, a lowering or raising of the chassis and nozzle relative to the rear wheels occurs when the rear axle 68 is turned in the bearings 66.

Formed in opposite sides of the access plate 30, just behind the nozzle openings 32 and 34, is a pair of front wheel recesses 88 and 90 within which respective front wheels 92 and 94 are positioned. A second and smaller pair of recesses 96 and 98 is formed in the access plate adjacent to, but behind, a respective one of the wheel recesses 88 and 90. The wheel 92 is rotatably mounted on one leg 100 of a U-shaped axle 102 having its second leg 104 positioned within the recess 96, and the wheel 94 is rotatably mounted on a leg 106 of a similar U-shaped axle 108 whose other leg 110 is positioned within the recess 98. At each side of the access plate, adjacent a respective recess 96 and 98, there is mounted a retaining plate 112 which is secured to the access plate by screws 114, thereby entrapping legs 104 and 110 within the respective recess 96 and 98, while allowing the legs 104 and 110 to be joumaled for pivotable movement. Thus, the front wheels 92 and 94, and their respective axes of rotation 100 and 106, may be raised or lowered relative to the chassis and the nozzle by pivoting about the respective journaled leg 104 and 110. Conversely, the nozzle may be lowered or raised by movement of the wheels 92 and 94 about legs 104 and 110, or movement of the chassis about legs 100 and 106. Retaining links 116 and 118 respectively secure wheels 92 and 94 against axial movement.

The front and rear wheel assemblies are interconnected at respective sides of the cleaner by linkage assemblies 120 and 122. Linkage assembly 120 includes a first link arm 124 having a hole 126 at one end thereof through which passes the offset end 72 of the rear wheel axle 68, and'a second link arm 128 secured to the arm 124 by a screw 130 adjacent one end thereof and includes a hole 132 at the other end thereof through which front axle leg 100 passes. Similarly, the linkage assembly 122 includes a link arm 134 having a hole 136 on the rear end thereof through which passes the offset portion 74 of the rear axle 68 while the other end of the link arm 134 is secured to one end of a second link arm 138 by means of a screw 140 and a hole not shown at the other end of link arm 138 receives the leg 106 of the axle 108 therethrough. A slot 144 in the link arm 138 is provided so that the relationship between the arms 134 and 138 may be adjusted at the factory to provide the proper movement of the wheel 94 and the wheel 86. The link arm 128 includes a similar slot (not shown) for the same purpose. Formed in the link arm 134 is a notch 146, the purpose of which will be hereinafter explained. It should, however, be apparent that the axes of rotation of all four wheels are simultaneously moved relative to the chassis and nozzle by the operation of the linkages 120 and 122. The combined length of the linkarms 134 and 138, and of the arms 124 and 128 are longer than the distancebetween the central portion 70 of the rear axle 68 and the legs 104 and 110 of the front axles 102 and 108; i.e., the lateral distance between the front and rear journals is less than the lateral distance between the axes of rotation of the front and rear wheels, and the front wheels pivot relative to the chassis about an axis 104 and 110 which is behind the axes of rotation 100 and 106 and the rear wheels pivot relative to the chassis about an axis 70 which is in front of the axes of rotation 72 and 74, so that any movement of the front wheels in an upwardly direction relative to the chassis and nozzle results in the rear wheels lowering relative thereto, and any lowering of the front wheels relative to the chassis and nozzle results in the rear wheels raising. The same result could occur if the lateral distance between the front and rear journals is greater than the lateral distance between the axes of rotation of the front and rear wheels if the front journals are in front of the front wheel axes and the rear journals are behind the rear wheel axes. In both cases the greater the difference between the axle journal distance and the wheel axis distance, the smaller the movement required for a given nozzle height variation.

In order to manually adjust the wheel assemblies there is provided an adjustment lever 148 comprising an arm 150 having a pair of bifurcated legs 152 and 154 integral with and spaced from the arm 150 by a transverse portion 156. The lever 148 further includes an integral bushing portion 158 extending from the transverse portion 156 at the side adjacent the arm 150. Extending through the transverse portion 156 and the bushing 158 is an aperture 160 through which a pin or axle 162 passes. The axle 162 is secured at one end in a hole in the chassis and is secured by a screw 164 in a flattened portion 166 at the other end thereof to a boss 168 on the bottom of the chassis. Another pin 170 passes through and extends between holes formed in the bifurcated legs 152 and 154 and is adapted to engage and fit within the notch 146 in the link 134. A lock spring 172 having a manually engageable handle portion 174 secured at one extremity thereof and a bent portion 176 having an aperture 178 at the other extremity thereof is positioned on the arm 150 by passing the arm through the aperture 178. The lock spring 172 includes two flanges 180 and 182 between which the arm 150 is positioned after passing through aperture 178, and also includes a slot 184, the purpose of which will presently be described. The arm 150 includes a groove adapted to receive the outer extremity of the aperture 178 of the bent portion 176 and acts as fulcrum for the spring. The upper portion of the chassis above the spring member includes an opening 186 through which the handle 174 and a portion of the spring flanges extend. Secured to a boss at the underside of the chassis by means of screws 188 is a step bracket 190 having a plurality of, preferably four, teeth 192, 194, 196, 198 extending horizontally from the upper portion thereof. The spring 172, as shown in FIG. 5, is bent away from arm 150 of lever 148 so that when it is positioned on the arm 150 it is biased such that the slot 184 is forced against the tooth portion of the bracket member 190. A manual force is, therefore, required to overcome the bias to disengage the spring from the teeth. Thus, the spring may be manually moved by means of the handle 174 to selectively engage the slot 184 with a desired one of the teeth 192, 194, 196, 198. Movement of the handle 174 in the plane of the paper as shown in FIG. 2 causes the adjustable lever 148 to turn about the shaft 162 thereby forcing the pin 170 to coact with the notch 146. This effects movement of the links 134 and 138 which causes all four wheels to pivot about their respective chassis mounting journals and thereby raises or lowers the chassis and the nozzle relative to the wheels and the floor surface upon which the wheels set.

In FIG. 2 the vacuum cleaner is illustrated in solid lines in the lowerest nozzle height position and the rear of the chassis is thus in its highest position. Inasmuch as this position is optimum for cleaning outdoor type carpeting, i.e., patio carpeting, the extension of the line of the bottom of the chassis is designated P. In order to raise the nozzle, the handle 174 is pushed outward away from tooth 192 and then moved clockwise toward one of the other teeth and is then released so that the slot 184 locks with the selected tooth. Each other tooth 194, 196, 198 corresponds with a fixed nozzle height position designated normal, high or shag for the various types of floor coverings. FIG. 2 illustrates in dotted lines the highest nozzle height corresponding to shag carpeting. The extension of the line of the bottom of the chassis at each of these detent positions is shown and designated N for normal carpeting, H for high pile carpeting, and S for the shag type carpeting. Of course, other nozzle heights are available by deploying more teeth on the bracket 190. However, it should be understood that by pivoting the chassis about both the front and rear wheels to effect a nozzle height change, a

reduced angular variation of the chassis relative to the,

floor results as compared to merely pivoting the chassis about either the front or rear wheels separately.

Numerous alterations of the structure herein disclosed will suggest themselves to those skilled in the art. However, it is to be understood that the present disclosure relates to a preferred embodiment of our invention which is for purposes of illustration only and not to be construed as a limitation of the invention. All such modifications which do not depart from the spirit of the invention are intended to be included within the scope of the appended claims.

Having thus set forth the nature of the invention, what is claimed herein is:

1. A nozzle height adjusting mechanism for a vacuum cleaner having a chassis including a suction nozzle inlet at the bottom thereof, said mechanism comprising in combination front and rear wheels for supporting said chassis for movement on a floor surface, front axle means having offset portions on which said front wheels are journaled and rear axle means having offset portions on which said rear wheels are journaled, said front axle means including journal portions turnably mounted on said chassis providing for movement of said front wheels toward and away from said chassis upon turning of said journal portions, said rear axle means including journal portions turnably mounted on said chassis providing for movement of said rear wheels toward and away from said chassis upon turning of said journal portions, linkage means interconnecting said offset portions of said front and rear axle means for simultaneous movement of saidfront wheels and said rear wheels indifferent vertical directions relative to said chassis, and adjustment means movable between a plurality of positions for selectively moving said linkage means to vertically move said front and rear wheels in different directions relative to the chassis, whereby said nozzle is vertically moved relative to the floor.

2. A nozzle height adjusting mechanism as recited in claim 1 wherein the distance between the offset portion of the front and rear axle means differs from the distance between the journal portions thereof.

3. A nozzle height adjusting mechanism as recited in claim 2 wherein said rear axle means comprises a rear axle extending from side to side of said chassis including a central portion, offset arms formed on opposite ends of said central portion, a rear wheel rotatably carried on each offset arm, said central portion having journal portions, spaced bearings on the rear of said chassis pivotably mounting said journal portions, said front axle means comprising a substantially U-shaped shaft at each side of said chassis, each shaft having one leg pivotably mounted on said chassis substantially parallel to the central portion of said rear axle, a front wheel rotatably carried on the other leg of each shaft, said linkage means comprising a linkage assembly at each side of said chassis, each linkage assembly operatively connecting an offset arm portion of said rear axle with a respective front wheel carrying leg.

4. A nozzle height adjusting mechanism as recited in claim 3 wherein said means for selectively moving said linkage means comprises a lever member, means pivotably mounting said member on said chassis, said member including a pin, the linkage assembly on at least one side of the chassis having a notch. formed therein for receiving said protrusion, and means for selectively pivoting said lever to move said linkage as sembly and thereby all said wheels.

5. A nozzle height adjusting mechanism as recited in claim 4 wherein said means for selectively pivoting said lever comprises a spring member having one end thereof fastened to said lever and a manually engageable handle mounted on its other end for moving said spring in a direction to pivot said lever, and means for locking said spring to said chassis, said spring being normally biased in the locking direction so that the bias must be manually overridden to move said spring in the pivoting direction.

6. A nozzle height adjusting mechanism as recited in claim 3 wherein the lateral spacing between the central portion of said rear axle and the pivotably mounted leg of each respective U-shaped shaft is smaller than the lateral spacing between each offset arm of the rear axle and the front wheel carrying leg of each respective U- shaped shaft. 7

7. A nozzle height adjusting mechanism as recited in claim 6 wherein said means for selectively moving said linkage means comprises a lever member, an axle mounted on one side of said chassis, said lever member being joumaled on said axle for pivotal movement relative to said chassis and having a pin spaced from and substantially parallel to said axle, the linkage assembly on said one side of the chassis including a notch for receiving said pin, a leaf spring fastened at one end to said lever and having a handle secured to its other end and extending through the chassis, detent means for locking said spring and lever against movement, said spring having a bend formed therein so that the spring is normally biased into locking relation with said means for locking and may be released therefrom by overriding said bias, whereby arcuate movement of said handle effects pivotal movement of said spring and lever about said axle and the linkage assembly on said one side of the chassis is moved by coaction of the pin and notch. 

1. A nozzle height adjusting mechanism for a vacuum cleaner having a chassis including a suction nozzle inlet at the bottom thereof, said mechanism comprising in combination front and rear wheels for supporting said chassis for movement on a floor surface, front axle means having offset portions on which said front wheels are journaled and rear axle means having offset portions on which said rear wheels are journaled, said front axle means including journal portions turnably mounted on said chassis providing for movement of said front wheels toward and away from said chassis upon turning of said journal portions, said rear axle means including journal portions turnably mounted on said chassis providing for movement of said rear wheels toward and away from said chassis upon turning of said journal portions, linkage means interconnecting said offset portions of said front and rear axle means for simultaneous movement of said front wheels and said rear wheels indifferent vertical directions relative to said chassis, and adjustment means movable between a plurality of positions for selectively moving said linkage means to vertically move said front and rear wheels in different directions relative to the chassis, whereby said nozzle is vertically moved relative to the floor.
 1. A nozzle height adjusting mechanism for a vacuum cleaner having a chassis including a suction nozzle inlet at the bottom thereof, said mechanism comprising in combination front and rear wheels for supporting said chassis for movement on a floor surface, front axle means having offset portions on which said front wheels are journaled and rear axle means having offset portions on which said rear wheels are journaled, said front axle means including journal portions turnably mounted on said chassis providing for movement of said front wheels toward and away from said chassis upon turning of said journal portions, said rear axle means including journal portions turnably mounted on said chassis providing for movement of said rear wheels toward and away from said chassis upon turning of said journal portions, linkage means interconnecting said offset portions of said front and rear axle means for simultaneous movement of said front wheels and said rear wheels indifferent vertical directions relative to said chassis, and adjustment means movable between a plurality of positions for selectively moving said linkage means to vertically move said front and rear wheels in different directions relative to the chassis, whereby said nozzle is vertically moved relative to the floor.
 2. A nozzle height adjusting mechanism as recited in claim 1 wherein the distance between the offset portion of the front and rear axle means differs from the distance between the journal portions thereof.
 3. A nozzle height adjusting mechanism as recited in claim 2 wherein said rear axle means comprises a rear axle extending from side to side of said chassis including a central portion, offset arms formed on opposite ends of said central portion, a rear wheel rotatably carried on each offset arm, said central portion having journal portions, spaced bearings on the rear of said chassis pivotably mounting said journal portions, said front axle means comprising a substantially U-shaped shaft at each side of said chassis, each shaft having one leg pivotably mounted on said chassis substantially parallel to the central portion of said rear axle, a front wheel rotatably carried on the other leg of each shaft, said linkage means comprising a linkage assembly at each side of said chassis, each linkage assembly operatively connecting an offset arm portion of said rear axle with a respective front wheel carrying leg.
 4. A nozzle height adjusting mechanism as recited in claim 3 wherein said means for selectively moving said linkage means comprises a lever member, means pivotably mounting said member on said chassis, said member including a pin, the linkage assembly on at least one side of the chassis having a notch formed therein for receiving said protrusion, and means for selectively pivoting said lever to move said linkage assembly and thereby all said wheels.
 5. A nozzle height adjusting mechanism as recited in claim 4 wherein said means for selectively pivoting said lever comprises a spring member having one end thereof fastened to said lever and a manually engageable handle mounted on its other end for moving said spring in a direction to pivot said lever, and means for locking said spring to said chassis, said spring being normally biased in the locking direction so that the bias must Be manually overridden to move said spring in the pivoting direction.
 6. A nozzle height adjusting mechanism as recited in claim 3 wherein the lateral spacing between the central portion of said rear axle and the pivotably mounted leg of each respective U-shaped shaft is smaller than the lateral spacing between each offset arm of the rear axle and the front wheel carrying leg of each respective U-shaped shaft. 